Metallic compounds adapted to form an electrical contact



Patented Nov. 5, 1 945 METALLIC COMPOUNDS ADAPTED TO FORM AN ELECTRICALCONTACT Irvin W. Cox, West Allis, Wis, assignor to-Cutler- Hammer, Inc.,Milwaukee, Wis, a corporation oFFicEi of Delaware.

No Drawing. Application October 10, 1942,. Serial No. 461,601

7: Claims. 1

This invention relates to improvements in metallic compounds. Theinvention also relates to bodiesconsisting of said metallic compounds.Although the compounds herein contemplated are adaptable for varioususes, they are particularly advantageous for use in the formation ofelectrical switch contacts and the like.

Although, as will appear, my invention is useful inthe formationof manydifferent metallic compositions,-it isparticularly useful andadvantageous in the formation of metallic compounds, havingalloycharacteristics, by the-use of metals or elements which will not allo inthe ordinary manner. Forexam-ple, I refer to a compoundof silver andmolybdenum, from which ingredients' an alloy, in the ordinary sense,cannot be produced. Inaccordance with my invention, however, suchnon-alloy-ableingredients m y be compounded in'a manner to obtainsubstantially all of the desirable characteristics of an alloy; such ashomogeneity of the mixture of the ingredients, proper proportionalitythereof, required hardness and electrical characteristics; etc.Moreover, in accordance with my invention the aforementioned desirableresults are attained by treatment of the ingredients of the compound ina relatively simple and inexpensive manner.

I will herein describe the method of producing one of the desiredcompounds of silver and molybdenum; but it is tobe understood that themethod or technique herein disclosed is likewise applicable totheproduction of other similar compounds of silver and molybdenum, and to aseries of compounds of silver and tungsten, silver and cobalt; as wellas to a series of compounds of:

Nickel and tungsten,

Nickel and molybdenum,

Cobalt and tungsten,

Cobalt,tungsten and carbon (cobalt tungsten carbide from cobalt tungstencyanide),

Cobalt, tungsten and chromium (stellite, from cobalt chromate and cobalttungsten. chromate),

Cobalt and molybdenum,

Copper and tungsten,

Copper and molybdenum,

Iron and tungsten,

Iron and molybdenum,

Manganese andtungsten,

Manganese and molybdenum.

and, in general, to suchv and other compounds containing atoms of. twoor more metals in each.

controlled reduction of well defined poly metallic salts, such as thoseof the acids of chromium,

molybdenum and tungsten by the use of hydrogen, hydrocarbon, orcarbonaceous gases; andthe invention also contemplates the controlledreduction by such agents of mixture of the aforementioned poly metallicsalts.

An object of the invention is to provide. metal-- 110 compounds havingmost. of the desirable characteristics of alloys.

Another object is to provide for alloy char-- acteristics in metalliccompounds the ingredients of which are unalloyable in the ordinarysense. v

Another and more specific object is to provide improved metalliccompounds adaptable for use in the production of electrical switchcontacts..-

Another object is to provide electrical switch: contacts and the like ofnovel composition.

Other objects and advantages of the invention will hereinafter appear.

One example of the method. herein contemplated is as follows: To a hotsaturated solution of para ammonium molybdate is added. a hot. so lutionof dilute silver nitrate, with resulting formation of a fine yellowprecipitate. Such precipitate is freed of ammonium nitrate in aWellknown manner, then dried, and then reduced in a. current or flow ofdry hydrogen in steps say, for about fifteen minutes at 400 degrees EL,then. for about fifteen minutes at 800 degrees F., after which thetemperature isgradually raised to about 1600 degrees F., at whichtemperature the reduction appears to be complete. The product of suchreduction is an extremely fine grained silvery powder: of constant orhomogeneous composition, in the sense that the finest particles thereofcontain the same proportions of silver and molybdenum as the coarsest.Powder produced in the manner just described showed a silver content of49.2 per cent by weight.

From the foregoing it. is obvious that the yel'-- low silver molybdate;(precipitate) was the para. salt corresponding to silver para ammoniummolybdate, or AgsMoqO24(H2O) X, and that the reduced powder is theequivalent of silver molybdide, of the formula AgGMO'I.

When such reduced powder is molded or com-' pressed into suitable formfor use as electrical contacts, a polished and etched specimen shows,under a microscope, an extremely fine structure; in which silver andmolybdenum are not distinguishable asseparate components. After themolded contacts have been annealed: at a temperature of 1200 degrees F.they have a hardness ofabout Rockwell B., but by aging the same forseveral hours at 600 degrees F. the hardness thereof is increased toabout 97 R. B. This hardening is, to a large. extent atleast, a strainhardening produced by the tendency toward precipitation of the silverfrom the silver molybdide of which the contact is composed.

The fact that the material produced in accordance with my invention is anew and different constitution of matter has been demonstrated by acomparison of a micro-photograph of such material with a similarmicro-photograph of a sin tered contact material made in the usual wayfrom substantially the same percentage content of the ingredients silverand molybdenum (namely, by mixing silver powder with molybdenum powder,and pressing and sintering the mixture).

The following is a partial list of the various silver salts ofmolybdenum and tungsten acids--the water of crystallization beingomitted from the formulae--and the final column showing the respectivemolybdides and tungstides:

The compounds of silver and molybdenum, silver and tungsten, and silverand cobalt produced in accordance with my invention are especiallyadapted for the production of electrica1 contacts or contact tips,inasmuch as the inherently fine and substantially perfect (molecular)distribution of the refractory metal lattice, molybdenum, tungsten orcobalt) enables its most efficient use; so that for a given hardness andare resisting capactiy a greater percentage of silver can be used thanhas heretofore been possible, with a consequent decrease in the contactresistance. Also, the aforementioned precipitation hardening which produces a strain in the silver enhances the conductivity of the latter.

After producing any one of the powders (molybdides, tungstides orchromides) in the manner herein disclosed I may add thereto andintimately mix therewith a powder of the particular soft metalconstituent thereof (such as silver, copper, nickel, cobalt, iron ormanganese) to increase the percentage quantity of such softer metal inthe final molded article. It is, of course, preferable to employ apowder obtained by the aforedescribed reducing operation whichapproXimates as closely as possible the desired percentages of themetallic ingredients in the final pressure molded and heat treatedarticle.

I claim:

1. As an article of manufacture, a powder adapted for molding underpressure into suitable form for use as an electrical contact, saidpowderconsisting of a homogeneous composition of silver and molybdenum whereinthe finest particles thereof contain the same proportions of silver andmolybdenum as the coarsest, whereby an inherently fine and substantiallyperfect distribw' tion of the molybdenum lattice is insured in themolded contact, said powder having a composition which is the equivalentof silver molybdide of the formula AgsMO'I.

2. As an article of manufacture, a powder form for use as an electricalcontact, said powder consisting of a homogeneous composition of silverand molybdenum wherein the finest particles thereof contain the sameproportions of silver and molybdenum as the coarsest, whereby aninherently fine and substantially perfect distribution of the molybdenumlattice is insured in the molded contact, said powder having acomposition which is the equivalent of silver molybdide of the formulaAgsMow, said powder having a silver content of 49.2 per cent by weight.

3. As an article of manufacture, a pressure molded electrical contactconsistin of a homogeneous powder composition of silver and molybdenumwherein the finest particles thereof contain the same proportions ofsilver and molybdenum as the coarsest, whereby an inherently fine andsubstantially perfect distribution of the molybdenum lattice in thecontact is insured, said powder composition being the equivalent ofsilver molybdide of the formula AgsMow.

4. As an article of manufacture, a pressure molded electrical contactconsisting of a homogeneous powder composition of silver and molybdenumwherein the finest particles thereof contain the same proportions ofsilver and molybdenum as the coarsest, whereby an inherently fine andsubstantially perfect distribution of the molybdenum lattice in thecontact is insured, said powder composition being the equivalent ofsilver molybdide of the formula AgeMo'z, and the silver content of saidcontact being 49.2 per cent by weight.

5. As an article of manufacture, a pressure molded electrical contactconsisting of a. homogeneous powder composition of silver and molybdenumwherein the finest particles thereof contain the same proportions ofsilver and molybdenum as the coarsest, whereby an inherently fine andsubstantially perfect distribution of the molybdenum lattice in thecontact is insured, said powder composition being the equivalent ofsilver molybdide of the formula AgsMov, the silver content of saidcontact being 49.2 per cent by weight, and said contact when annealed ata temperature of 1200 degrees F. having a hardness of about 75 RockwellB.

6. As an article of manufacture, a pressure molded electrical contactconsisting of a homogeneous powder composition of silver and molybdenumwherein the finest particles thereof contain the same proportions ofsilver and molybdenum as the coarsest, whereby an inherently fine andsubstantially perfect distribution of the molybdenum lattice in thecontact is insured, said powder composition being the equivalent ofsilver molybdide of the formula AgeMov, the silver content of saidcontact being 49.2 per cent by weight, said contact when annealed at atemperature of 1200 degrees F. having a hardness of about '75 RockwellB., and said contact when aged for several hours at 600 degrees F.having a hardness of about 97 Rockwell B.

7. As an article of manufacture, a pressure molded electrical contactconsisting of a homogeneous powder composition of silver and molybdenumwherein the finest particles thereof. contain the same proportions ofsilver and molybdenum as the coarsest, whereby an inherently fine andsubstantially perfect distribution of the molybdenum lattice in thecontact is insured, so that for a given hardness and are resistingcapacity an extremely high percentage of silver may beutilized.

'IRVIN w. ooxd

